{"id":371539,"date":"2024-07-12T00:34:54","date_gmt":"2024-07-12T00:34:54","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/two-way-fsi-its-impossible-to-simulate-a-cantilever-discharging-pipe-in-ansys\/"},"modified":"2024-07-12T00:34:54","modified_gmt":"2024-07-12T00:34:54","slug":"two-way-fsi-its-impossible-to-simulate-a-cantilever-discharging-pipe-in-ansys","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/two-way-fsi-its-impossible-to-simulate-a-cantilever-discharging-pipe-in-ansys\/","title":{"rendered":"Two-way FSI: It&#8217;s impossible to simulate a cantilever discharging pipe in Ansys"},"content":{"rendered":"<div>Hi everyone,<\/div>\n<div>&nbsp;<\/div>\n<div>For the past couple of months, I&rsquo;ve been trying to validate a discharging cantilever pipe experiment <strong>subjected to vertical gravity<\/strong> using <strong>ANSYS 2022R1<\/strong> system coupling in the Workbench. Here are the properties:<\/div>\n<div>\n<ul>\n<li>internal fluid: water&nbsp;<\/li>\n<li>pipe length: 94 mm<\/li>\n<li>inner radius: 1.36 mm<\/li>\n<li>outer radius: 1.66 mm<\/li>\n<li>E = 5.4 MPa<\/li>\n<li>pipe density = 5554 kg\/m3<\/li>\n<li>Poisson&#8217;s ratio: 0.33<\/li>\n<li>total run time: 0.5 sec<\/li>\n<\/ul>\n<p>The image below shows the experimental deflection of the pipe from this <a title=\"Deformations of an elastic pipe submitted to gravity and internal fluid flow\" href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0889974615000651?casa_token=HwkNYlBdAbIAAAAA:i67PLJbIxl3_l9bEPF1hky8ylrkxU69_xcnKitwEET1ktPjFk7KiCiR6XOMiFTns9xnfw0lLOA\" target=\"_blank\" rel=\"noopener\">article<\/a>.&nbsp;<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720743326-pipe expriment.PNG\" alt=\"\"><img decoding=\"async\" title=\"Static deflection of the cantilever pipe\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720743340-pipe shape.PNG\" alt=\"\"><\/p>\n<p>I want to derive the transverse deformation of the pipe due to the internal flow with a velocity of 2 m\/s. However, I&#8217;ve faced multiple types of error during my attempts. It is worth noting that the simulations worked with stiffer materials like aluminum alloy or structural steel.&nbsp;<\/p>\n<p>At first, I tried with Fluent-Mechanical:&nbsp;<\/p>\n<ul>\n<li>I followed the Workbench FSI tutorial.&nbsp;<\/li>\n<li>Encountered negative volume mesh errors around t = 3.3 ms<\/li>\n<li>Tried multiple timesteps ranging from 0.0001 to 1 microsecond, but the simulation didn&rsquo;t improve.<\/li>\n<li>Changed the dynamic meshing method from diffusion to linear elastic and set the outlet as unspecified, but no change.<\/li>\n<\/ul>\n<p>And currently changed to CFX-Mechanical, but the situation were worse:<\/p>\n<ul>\n<li>The solution doesn&rsquo;t progress after 3 to 4 iterations.<\/li>\n<li>common errors: &ldquo;MAPDL solution terminated due to DOF LIMIT EXCEEDED&rdquo; or mechanical force convergence value does not converge, causing unending iterations.<\/li>\n<li>large deflection was always ON<\/li>\n<\/ul>\n<p>My overall guess is that the time-step is not the issue. I also, read from the manual that larger mesh cells absorb most of the deformations while smaller ones experience rigid body motion, but I want to avoid adding a surrounding air volume as it introduces complexities due to two-phase interactions.<\/p>\n<p>I&#8217;d appreciate a lot if anybody has any idea how to solve this issue. <strong>The case itself is very simple and easy to try.&nbsp;<\/strong><\/p>\n<p>Some other details and images:&nbsp;<\/p>\n<ul>\n<li><strong>Pipe Mesh<\/strong>: Aspect ratio about 2, minimum element quality = 0.77.<\/li>\n<li><strong>Fluid Mesh<\/strong>: Maximum aspect ratio is 8.75 (most around 2.5 to 3.5), minimum element quality = 0.28.<\/li>\n<li>I added a fluid volume upstream of the pipe to make sure the flow inside the pipe is fully developed from the start.<\/li>\n<\/ul>\n<p>The whole geometry:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720744072-pipe_geom.PNG\" alt=\"\" width=\"699\" height=\"376\"><\/p>\n<p>Solid mesh:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"Solid pipe mesh\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720743943-solid-mesh.png\" alt=\"\" width=\"907\" height=\"344\"><\/p>\n<p>Fluid mesh:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720744004-fluid-mesh.png\" alt=\"\" width=\"916\" height=\"347\"><\/p>\n<p>The mechanical setup:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/innovationspace.ansys.com\/forum\/wp-content\/uploads\/sites\/2\/2024\/07\/12-07-2024-1720744118-mechanical-configs.png\" alt=\"\" width=\"792\" height=\"300\"><\/p>\n<\/div>\n","protected":false},"template":"","class_list":["post-371539","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["435731","281137","805"],"_bbp_author_ip":["70.30.211.66"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_bbp_likes_count":["1"],"_btv_view_count":["155"],"_bbp_topic_status":["unanswered"],"_bbp_topic_id":["371539"],"_bbp_forum_id":["27792"],"_bbp_engagement":["805","281137","435731"],"_bbp_voice_count":["3"],"_bbp_reply_count":["9"],"_bbp_last_reply_id":["373164"],"_bbp_last_active_id":["373164"],"_bbp_last_active_time":["2024-07-23 07:37:13"]},"test":"hossein-hashemidehaghimail-concordia-ca"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/371539","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/371539\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=371539"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}